Filtering circuit and power supply device equipped with same

ABSTRACT

The invention provides a filter circuit comprising inductors ( 6, 15 ) and capacitors ( 11 ) interconnected to form filter stages, the capacitors ( 11 ) being distributed over at least two printed circuit cards ( 7, 8 ) disposed facing each other and spaced apart by a gap (H), at least one inductor ( 15 ) extending across the gap (H) between the cards and connected to both cards ( 7, 8 ). The invention also provides a power supply device equipped with such a filter circuit.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a National Stage of Application PCT/FR02/00098,filed Jan. 11, 2002, incorporated herein by reference in its entirety.

BACKGROUND

The invention relates to a filter circuit and to a power supply deviceequipped with such a filter circuit. In the automotive field, more andmore high power electrical actuators are being used. In order to powersuch actuators, it is known to use a power supply device comprisingactuator control modules placed on a printed circuit card, together witha filter circuit comprising inductors and capacitors interconnected toform filter stages and also placed on the same card.

The inductors of a filter circuit suitable for conveying high powers arelarge in size. These components are generally placed parallel to thecard and therefore occupy a significant area thereof. Since card area islimited, the inductors are sometimes mounted on the face opposite fromthe face which receives the control modules. That disposition makesassembly the card more complicated and causes it to have thickness thatmakes it awkward to integrate in compact power supply devices.

Proposals have also been made to place the inductors perpendicularly tothe card, the connections with the printed circuit being adjacent toeach other. Such a structure presents a major risk of stray capacitancebetween the connections.

SUMMARY

In order to make the filter circuit more compact, the invention providesa filter circuit in which the capacitors are distributed over at leasttwo printed circuit cards placed facing each other and spaced apart by adetermined gap, and in which at least one inductor extends across thegap between the cards and is connected to both cards.

Thus, the area occupied by the inductors on the cards is restricted tothe area needed for connecting them, whereas the total are occupied bythe capacitors is distributed over both cards. The area occupied by thefilter circuit is thus considerably minimized. The inductor andcapacitor components of the filter circuit can thus be placed on thesame faces of the cards as the control modules.

In addition, the inductors then have electrical connections situated oneach card. These connections are thus spaced apart from each other by adistance equal to the length of the inductor, thereby minimizing anyrisk of stray capacitance between said two connections.

Advantageously, each inductor extending across the gap between the cardscomprises a stack of rings, at least one of which is made offerromagnetic material, said stack being disposed around a conductor barfixed to both cards. This provides an inductor that is compact and thatenables a high current to be passed. In addition, such a structure isstrong enough to act as a spacer between the two cards.

Advantageously, the filter circuit includes a common mode input stagewhich comprises an input inductor comprising a stack of rings, at leastone of which is made of ferromagnetic material, said stack being placedaround two parallel conductor bars fixed to one of the cards andextending across the gap between the cards, the bars being connected toa capacitor carried by the card to which the bars are fixed. Thisprovides a common mode input stage that is particularly compact.

Also advantageously, the filter circuit includes at least onedifferential mode stage which comprises both a conductor rod and anassociated inductor extending across the gap between the cards, theconductor rod and the inductor being connected to a capacitor carried byone of the cards. It is possible to build up a cascade of filter stagesin this way in which the capacitors are carried in alternation by eachof the cards.

Advantageously, the filter circuit has two output conductor rodsconnected to the capacitor of the last differential mode stage and fixedto both cards, extending across the gap between the cards. This makes itpossible to distribute the output power of the filter circuit over bothcards.

Advantageously, the output conductor rods are connected to twocapacitors each carried by a respective card. This disposition providesbetter distribution of the area occupied on the cards by the capacitors.

In another aspect the invention provides a power supply devicecomprising control modules connected to a filter circuit of theinvention, the control modules being disposed on facing faces of theprinted circuit cards of the filter circuit.

The control modules are thus distributed over the two cards, therebyreducing the bulk of the power supply device. In addition, the controlmodules and the inductors of the filter circuit, i.e. the bulkycomponents of the power supply device, are all contained in the gapbetween the cards. The housing of the power supply device can thus bedesigned to fit very closely around the outside faces of the cards,thereby reducing the overall size of the power supply device.

It is then advantageous for at least one cooling pipe to extend betweenthe two cards in the vicinity of the control modules. The cooling pipeis thus efficient at picking up the heat given off by the controlmodules.

Advantageously, flexible heat sinks are connected to the cooling pipeand disposed around the inductors of the filter circuit. The heat givenoff by the inductors is thus picked up and conveyed to the cooling pipe,even when the inductors are not immediately adjacent to the coolingpipe.

BRIEF DESCRIPTION OF THE DRAWINGS

Other characteristics and advantages of the invention appear moreclearly in the light of the following description of a particular,non-limiting embodiment of the invention, given with reference to theaccompanying drawings and figures, in which:

FIG. 1 is a partially cutaway diagrammatic perspective view of a filtercircuit of the invention, showing how the electrical components aredistributed between the two printed circuit cards;

FIG. 2 is an exploded perspective view of a fraction of the inductorsand the conductor rods of the filter circuit; and

FIG. 3 is a perspective view of a power supply device of the inventionequipped with the filter circuit shown above.

MORE DETAILED DESCRIPTION

With reference to FIG. 1, a filter circuit 1 comprises in conventionalmanner inductors 15, capacitors 11, and conductors 14 arranged in asuccession of filter stages, beginning with a common mode stage MC, andfollowed by one or more differential mode stages MD.

The filter circuit 1 comprises an input inductor 6 having two inputterminals 2 and 3. In the invention, the input inductor 6 extends acrossa gap H between two printed circuit cards 7 and 8 that are placed facingeach other, in this case parallel to each other. The input inductor 6has two ends 9 and 10 connected to the card 8. Each of the ends 9 and 10is connected via a respective conductor track to one terminal of arespective capacitor 11.a carried by the card 8, the other terminals ofthese capacitors being connected to a support chassis for the cards 7and 8 (not shown) in order to be grounded. The ends 9 and 10 are alsoconnected to respective terminals of a capacitor 11.c carried by thecard 8 so as to co-operate with the capacitors 11.a and the inductor 6to form the common mode stage MC of the filter circuit. The terminals ofthe capacitor 11.c form the output terminals of the common mode stageMC.

The output terminals of the common mode stage MC are connected to afirst differential mode filter stage MD1 comprising an inductor 15 givenparticular reference 15.1 in order to enable it to be identifiedindividually, and a conductor 14, more particularly a conductor rod14.1. The inductor 15.1 and the conductor rod 14.1 extend across the gapH between the cards and they are connected to both cards 7 and 8. Theconductor rod 14.1 and the inductor 15.1 are connected on the card 8 tothe capacitor 11.c of the common mode stage MC. The conductor rod 14.1and the inductor 15.1 are connected on the card 7 to a capacitor 11.1 soas to co-operate therewith to form the first differential mode stageMD1. The terminals of the capacitor 11.1 form the output terminals ofthe first differential mode stage MD1. A series of differential modestages are made in the same manner, with the figure showing only thestage MDn preceding the final stage MDF.

For each differential stage, the capacitors 11.1 of the filter circuitare thus distributed in alternation on the cards 7 and 8, and preferablyon the facing faces of the cards, while the inductors 15.n and theconductor rod 14.n extend across the gap H between the cards. Theinductances of the inductors and the capacitances of the capacitors canvary from stage to stage, but they are preferably identical in order tosimplify assembly.

The filter circuit is terminated by a final differential mode stage MDFcomprising a conductor rod 14.f and an inductor 15.f extending acrossthe gap H between the cards and connected to both cards 7 and 8. Theconductor rod 14.f and the inductor 15.f are connected to two outputconductor rods 21 and 22 between which capacitors 11.7 and 11.8 carriedrespectively by the cards 7 and 8 are connected. The capacitors 11.7 and11.8 are thus connected in parallel and are equivalent to a singlecapacitor of capacitance equal to the sum of the capacitances of twocapacitors 11.7 and 11.8. This disposition serves to distribute thecapacitors of the final stage MDF forming the output capacitance of thefilter circuit, and thus serves to distribute in analogous manner theoutput power of said circuit over both cards.

In a preferred embodiment shown in FIG. 2, the conductor rods 14 aregenerally circularly cylindrical in shape, each comprising a pin 41soldered at one end to one of the cards, in this case the card 8. Inthis case, the pin 41 has a tripod with legs 42 received in shapedorifices in the card 8. The legs 42 are designed to pass through thecard 8 so that they can be flow-soldered to conductor tracks (notvisible) made on the face of the card 8 opposite from its face receivingthe conductor rod 14.

The conductor rod 14 extends perpendicularly to the cards 7 and 8 acrossthe gap H between the cards. It is fixed to the card 8 by a screw 43carrying a washer 44 providing mechanical support, and also electricalconnection with a conductor track (not shown) formed on the outside faceof the card 7. The term “outside face” is used in the presentspecification to mean that face of a card which is not facing a face ofthe other card.

An inductor 15 comprises a conductor bar 51, one end of which can beseen in FIG. 2 projecting beyond a stack of rings 57. The conductor bar51 has a connection pin 52 soldered to the card 8 and its opposite endis fixed by means of a screw 53 for connection with the card 7.

Rings 57 of ferromagnetic material are placed around the conductor bar51. The rings 57 co-operate with the conductor bar 51 to form aninductor. In order to vary inductance, it is possible to vary the sizeof the rings 57, the number of the rings, or the magnetic permeabilityof the material from which they are made. If the height of theferromagnetic rings is not sufficient to cover the full height of theconductor bar 51, the ferromagnetic rings can be held in place withmagnetically permeable rings so as to prevent any movement of the rings57 on the conductor bar 51.

Using the same design, the input inductor 6 has two parallel conductorbars 61 and 62. The conductor bars 61 and 62 are placed facing eachother and they are surrounded by ferromagnetic rings 67. This provides afilter inductor in common mode.

Each of the conductor bars 61 and 62 carries one of the input terminals2, 3 of the filter circuit 1. The opposite ends of the conductor bars 61and 62 are connected to the card 8 by connection means of a typeessentially similar to that used for connecting the conductor rods 14 tothe card 8. The input inductor 6 in this case is taller than the gap Hbetween the cards, so a recess 68 is provided in the card 7 to allow itto pass through.

The inductors 15 and the conductor rods 14 are connected, as describedabove, to the capacitors 11 carried by the facing faces of the cards 7and 8. The capacitors 11 are represented symbolically by rectangularblocks, and they are much smaller in size than the inductors which areadapted to carry high power levels, and as a result the capacitorsoccupy only a small area on the cards 7 and 8. The capacitors 11 can bestacked on one another in order to adjust the capacitance they present,and also reduce the area they occupy on the cards.

FIG. 3 shows a power supply device of the invention comprising an inputfilter circuit 1 disposed between two cards 7 and 8 in the arrangementdescribed with reference to the two preceding figures. The cards 7 and 8of the filter circuit 1 are equipped with control modules 80 generallyin the form of rectangular blocks. There are four control modules 80 inthis case and they are arranged two per card on the facing faces of thecards 7 and 8, i.e. on the same faces as carry the capacitors 11 of thefilter circuit 1. Each control module 8 is juxtaposed with its neighboron the same card via a long side, and each control module 80 facesanother control module on the other card.

The control modules 80 receive power via the filter circuit 1, and eachof them delivers power to a group of power actuators (not shown) towhich the power supply device is connected. Each of the control modules80 is fitted with an output filter 90. Only one of the output filters 90is shown in the figure. The output filter 90 is made up of inductors 91of traditional type comprising a conductor wound around a ferromagnetictorus. The inductors 91 are much smaller in size than the inductors ofthe filter circuit 1, since the power they convey is considerablysmaller than the power which passes through the filter circuit 1. Theinductors 91 are disposed on a card in the vicinity of the associatedcontrol module. A zone represented in FIG. 3 by a shaded area 92 isreserved on the side of a card beside a filter 90 in order to enable aconnector (not shown) to be installed thereon, thus enabling theconductors to be connected to a cable for taking the power from thecontrol module 80 via the filter 90 to the actuators.

In order to cool the power supply device, a cooling pipe 100 is arrangedto extend between the cards 7 and 8. The pipe 100 is of flat rectangularsection so as to pass between the four control modules 80 carried by thecards, and so as to come into contact with the control modules 80. Thisdisposition of the pipe 100 provides large amounts of heat exchange areawith the control modules 80. Heat exchange is further increased by theflat shape of the pipe 100. The cooling fluid flowing in the pipe 100takes away a fraction of the heat generated by the control modules 80 inoperation.

The inductors of the filter circuit 1 are quite far away from the pipe100 because they are located on one edge of the cards 7 and 8. In orderto cool them, a flexible heat sink 101 connected to the pipe 100 isplaced around each of the inductors 6 and 15 in order to carry away afraction of the heat they generate and take it to the pipe 100.

The invention is not limited to the particular embodiment describedabove, but on the contrary covers any variant coming within the scope ofthe invention as defined by the claims.

In particular, although the filter circuit of the invention is describedwith inductors and conductor rods extending perpendicularly to thecards, these elements could extend between the facing cards at aninclined angle in order to optimize the volume occupied by the powersupply device, while also accommodating the length of the inductors. Forthis purpose, it is possible, if necessary, to provide different anglesof inclination depending on the positions of the inductors.

Although the filter circuit of the invention is shown with two cardsonly, the architecture of the filter circuit can be adapted to the shapeof the volume available for receiving the filter circuit, for example byproviding more than two cards located at different levels, with theconductor rods and the inductors extending across the gaps between thepairs of adjacent cards.

Although the inductors and the conductor rods are described as beinggrouped together in a zone of limited area of the cards, these elementscould be dispersed so as to cause them to act mechanically as spacersbetween the cards.

Although the filter circuit described above is applied to a power supplydevice, the same architecture could also be applied in other fields ofelectronics which require the use of filters.

1. A filter circuit comprising: inductors and capacitors connected toform filter stages, wherein the capacitors are distributed over at leasttwo printed circuit cards that are disposed facing each other, whereinat least one inductor extends across a gap between two of the at leasttwo printed circuit cards and is connected to both of the two printedcircuit cards between which it extends; and wherein each inductorextending across the gap comprises a stack of rings at least one ofwhich is made of ferromagnetic material, said stack being disposedaround a conductor bar fixed to both of the two printed circuit cards.2. A filter circuit according to claim 1, further comprising two outputconductor rods fixed to two of the at least two printed circuit cardsand extending across the gap.
 3. A filter circuit according to claim 2,wherein the conductor rods are connected to two capacitors each of whichis carried by a respective one of the two of the at least two printedcircuit cards.
 4. A filter circuit according to claim 1, wherein atleast one inductor or one conductor rod extending across the gap isperpendicular to the two of the at least two printed circuit cards.
 5. Afilter circuit according to claim 1, further comprising a common modeinput stage comprising the input inductor comprising the stack of rings,the bars being connected to a capacitor carried by the one of the atleast two printed circuit cards to which the two conductor bars arefixed.
 6. A filter circuit according to claim 1, further comprising atleast one differential mode filter stage comprising both a conductor rodand an associated inductor extending across the gap, the conductor rodand the inductor being connected to a capacitor carried by one of the atleast two printed circuit cards.
 7. A filter circuit according to claim1, further comprising at least one pipe of a cooling circuit thatextends between two of the at least two printed circuit cards in thevicinity of the control modules.
 8. A filter circuit according to claim7, further comprising flexible heat sinks connected to at least one ofthe at least one pipe and disposed around the inductors of the filtercircuit.
 9. A filter circuit according to claim 7, further comprising atleast one differential mode filter stage comprising both a conductor rodand an associated inductor extending across the gap, the conductor rodand the inductor being connected to a capacitor carried by one of the atleast two printed circuit cards.
 10. A filter circuit comprising:inductors and capacitors connected to form filter stages, the capacitorsbeing distributed over at least two printed circuit cards that aredisposed facing each other; a common mode input stage comprising aninput inductor comprising a stack of rings, at least one of which ismade of ferromagnetic material, said stack being placed around twoparallel conductor bars fixed to one of the at least two printed circuitcards and extending across the gap, the bars being connected to acapacitor carried by the one of the at least two printed circuit cardsto which the two conductor bars are fixed; wherein at least one inductorextends across a gap between two of the at least two printed circuitcards and is connected to both of the two printed circuit cards betweenwhich it extends.
 11. A filter circuit comprising: inductors andcapacitors connected to form filter stages, at least one differentialmode filter stage comprising both a conductor rod and an associatedinductor extending across the gap, the conductor rod and the inductorbeing connected to a capacitor carried by one of the at least twoprinted circuit cards; wherein the capacitors are distributed over atleast two printed circuit cards that are disposed facing each other; andwherein at least one inductor extend across a gap between two of the atleast two printed circuit cards and is connected to both of the twoprinted circuit cards between which it extends.
 12. A power supplydevice comprising: a filter circuit comprising inductors and capacitorsconnected to form filter stages, the capacitors being distributed overat least two printed circuit cards that are disposed facing each other;control modules connected to the filter circuit, the control modulesdisposed on facing faces of printed circuit cards of the filter circuit;wherein at least one inductor extends across a gap between two of the atleast two printed circuit cards and is connected to both cards; andwherein each inductor extending across the gap comprises a stack ofrings at least one of which is made of ferromagnetic material, saidstack being disposed around a conductor bar fixed to both of the twoprinted circuit cards.
 13. A power supply device according to claim 12,further comprising at least one pipe of a cooling circuit that extendsbetween two of the at least two printed circuit cards in the vicinity ofthe control modules.
 14. A power supply device according to claim 13,further comprising flexible heat sinks connected to at least one of theat least one pipe and disposed around the inductors of the filtercircuit.
 15. A power supply device according to claim 12, furthercomprising a common mode input stage comprising the input inductorcomprising the stack of rings, the bars being connected to a capacitorcarried by the one of the at least two printed circuit cards to whichthe two conductor bars are fixed.
 16. A power supply device according toclaim 15, at least one differential mode filter stage comprising both aconductor rod and an associated inductor extending across the gap, theconductor rod and the inductor being connected to a capacitor carried byone of the at least two printed circuit cards.
 17. A power supply deviceaccording to claim 12, at least one differential mode filter stagecomprising both a conductor rod and an associated inductor extendingacross the gap, the conductor rod and the inductor being connected to acapacitor carried by one of the at least two printed circuit cards. 18.A power supply device comprising: a filter circuit comprising inductorsand capacitors connected to form filter stages, the capacitors beingdistributed over at least two printed circuit cards that are disposedfacing each other; control modules connected to the filter circuit, thecontrol modules disposed on facing faces of printed circuit cards of thefilter circuit; and at least one pipe of a cooling circuit that extendsbetween two of the at least two printed circuit cards in the vicinity ofthe control modules; wherein at least one inductor extends across a gapbetween two of the at least two printed circuit cards and is connectedto both cards.
 19. A power supply device according to claim 18, furthercomprising flexible heat sinks connected to at least one of the at leastone pipe and disposed around the inductors of the filter circuit.